The present invention relates to the preparation of colloidal solutions. More particularly, the invention relates to a method for the preparation of a semitransparent colloidal solution of bismuth sodium tartrate with an extended, stable shelf life.
Elixir of bismuth has been known at least since the 1936 National Formulary for treatment of various maladies of the gastrointestinal tract, including acid indigestion. According to the 1936 National Formulary, elixir of bismuth is produced by diluting a quantity of glycerite of bismuth and adding further quantities of glycerin and aromatic elixirs as preservative agents. The glycerite of bismuth, as produced according to the 1936 National Formulary, generally comprises a milky colloidal solution of bismuth sodium tartrate.
Unfortunately, the National Formulary has failed to provide an accurate method for testing the strength of the glycerite of bismuth and has also failed to suggest methodologies for elimination of aromatic elixirs. As a result, the elixir of bismuth has to date been difficult and unnecessarily expensive to produce in desired strength.
It is therefore an overriding object of the present invention to improve over the methods of the prior art by presenting a method whereby bismuth sodium tartrate may be produced in a semitransparent colloidal solution, which solution may be accurately and safely tested for strength of active ingredient. It is a further object of the present invention to present such a method wherein the resulting elixir may be expected to have an extended shelf life. Finally, it is yet another object of the present invention to present such a method wherein regulated ingredients, such as aromatic elixirs, may be eliminated from the formula without compromise of product integrity.
In accordance with the foregoing objects, the present inventionxe2x80x94a method for preparation of a semitransparent colloidal solution of bismuth sodium tartratexe2x80x94generally comprises the steps of producing an aqueous solution of bismuth sodium tartrate; extracting a magma of bismuth sodium tartrate from the aqueous solution at a pH of approximately 2.2; and then dissolving the magma into a salting-in mixture to form the semitransparent colloidal solution of bismuth sodium tartrate. It is critical to the present invention that the magma be extracted at a pH of at least 2.2 but not more than 2.3. As a result, in the preferred method of the present invention, the magma is extracted by washing with a wash liquor comprising an addition of distilled water; allowing the magma to settle out of the wash liquor; measuring the pH of the wash liquor after the magma has settled; and then decanting the wash liquor from the magma. This process is then repeated as necessary to arrive at a magma within the critical pH range, whereafter the magma is air dried in preparation for salting-in.
In the preferred method of the present invention, the salting-in solution is prepared by heating a quantity of distilled water; dissolving a quantity of sodium bicarbonate into the heated quantity of distilled water; and then mixing a quantity of tartaric acid with the solution of sodium bicarbonate and heated distilled water. In this manner, freezing of the salting-in solution is prevented, thereby ensuring a proper mixture.
The preferred method of the present invention further comprises the step of pasteurizing the semitransparent colloidal solution of bismuth sodium tartrate in order to eliminate the need for aromatic elixirs without compromise of product purity. In order to prevent damage to the active ingredient, however, the pasteurizing step comprises raising the semitransparent colloidal solution of bismuth sodium tartrate to a temperature of approximately 54.5xc2x0 C.; holding the solution at the pasteurization temperature for at least five but not more than eight minutes; and then returning the solution to ambient temperature.
The resulting semitransparent solution may then be tested for strength utilizing spectral methods. In at least one implementation of the present invention, this may comprise the steps of measuring a quantity of light transmitted through a sample of the semitransparent colloidal solution of bismuth sodium tartrate; converting the measured quantity of light to an indicium of the density of active ingredient present within the solution; and then calculating the per unit quantity of bismuth trioxide present.
The preferred method of the present invention also comprises diluting the base solution to an elixir strength according to the tested strength of the base. It is critical, however, that the dilute elixir be buffered to a critical pH range in order to sustain prolonged shelf life without degradation of the semitransparent nature of the product. In particular, sodium bicarbonate is added to the end product to achieve a final pH of about 7.2 to 7.3.
Finally, many other features, objects and advantages of the present invention will be apparent to those of ordinary skill in the relevant arts, especially in light of the foregoing discussions and the following drawings, exemplary detailed description and appended claims.